Photodechlorination of polychlorobenzene congeners in surfactant micelle solutions

Photochemical reactions of polychlorobenzene congeners in aqueous solutions containing surfactant micelles have been investigated. All photolysis experiments were performed with a Rayonet RPR-100 merry-go-round photoreactor utilizing 253.7-nm monochromatic ultraviolet (UV) lamps. Photoreduction through photodechlorination was shown to be the main decay pathway in which lesser chlorinated congeners and benzene were formed as intermediates. Final products included H+and Cl-in approximately stoichiometric amounts. In addition, some minor pathways were observed including photochlorination (the reverse reaction), photoisomerization, and finally photohydrolysis, through which phenol was formed. The quantum yield for the decay of hexachlorobenzene was found to be about an order of magnitude greater in micellar solutions than in water alone. Several hydrogen sources were investigated with sodium borohydride shown to be a promising rate enhancer at elevated concentrations.